Light-sensitive cell



May 14, 1935- E A. w. CARPENTER 2,001,672

LIGHT SENSITIVE CELL Filed sept. 2o, 1930 @QZ a 5 4 f I A M *e4 )ff M if INVENTOR AFT/fw? /4/ @1ERE/v 727? ylo `Patented May 14, 1935 UNITED STATESv PATENT OFFICE 2,001,672 s l LIGHTLsENsITrvE CELL Arthur W. Carpenter, New Yorlr, N. Y., assigner to United Research Corporation, New York, N. Y., a corporation of Delaware l Application september zo, 1930, serial No. 433,263

1 Claim.

and particularly to means for increasing the response of a cell to a given light intensity.

be obtained in order tosecure a substantial lectrical output from the cellv and to secure reduced losses therein for a given value of illumination.

An object of this invention is response of a light-sensitive cell intensity. Y

Another object is to avoid the to increase the to a given light loss of response in a light-sensitive cell from unabsorbed light when the sensitive layer is thin and not opaque.

Still another object is to combine in a lightsensitive cell a plurality of sensitive members responsive tothe same beam of light.

A further object is to combine in a light-sensitive cell a light-sensitive layer and a re'ector.

member.

still further objects are to combines pmrauty 1 of separated cell members into a responsive to a single light beam, and toutilize a member having electrodes and sensitive layers on both. sides.

single structure,A

In the operation of light-sensitivecells'it is found that when the thickness of the coating of sensitive material is. made of su ch a value, that is, thin enough,` to secure the maximum ratio between the average resistance of the cell, andthe,

change. in resistance with a givenintensity of illumination, a substantial port1 on of the light incident upon the cell passes through the sensitive material, because of the transparency inherent in a thin coating. This 'the production of response light-sensitive cell.`

This invention provides means light` is lost for in the usual type of for utiiizinthis methods.

These objects are thus accomplished by causing a beam ofL light to be successi ely partially absorbed and converted into elect cal response.

Other objects and structural details of the yinvention will be apparent from the following description when read in connection with the^ac companying drawing wherein:

, m. 1 is a view in vertical section of a. iightsensitive cell according to the ing a reilecting means. 1,

invention, embodyng. z is s view also in vertical section, or a .tions `over which is positioned a layer of photo- I (Cl. 201-63) 'Ihis invention relates to light-sensitivecells,

light-sensitive cell embodying a plurality of layers of sensitive material.

Fig. 3 is a view in vertical section of a lights'ensitive cell embodying a plurality of layers of light-sensitive material adapted to multiple reflection of light between various surfaces, and

Fig. 4 is a view in vertical section along the lines l-l of the cell shown in Fig. 3.

Referring tothe gures, particularly to Fig. 1, a glass plate or slip I is provided, upon which isV mounted a pair of electrodes 2 and"3, preferably of platinum and adherent to the glass I.- The electrodes .are provided with interdigitated porsensitive material 4 such as selenium. l The sensitive material 4 is covered and protected by a cup member 5 held in. place by cement 6. Within the cup 5 is positioned a quantity of appropriate dryingk material such as calcium chloride l for aiding in the protection of the light sensitive material I, and also a reflector means which may conveniently consist of glass or other suitable material 8 upon which is a reflecting surface 9. If the member 8 is of glass, the reflecting surface 9 may be a silver'lm on the side opposite to the sensitive material l. If the material 8 is an opaque substance as steel, ete., the reflecting surface 9 should obviously be upon the same vside as the sensitive material I. The reflector member may be held in position by the cement I0 asshown,

kor may be simply laid loosely within the cup member 5 upon the drying material -1. In

any event, care should be taken that the cement I 0 does not produce an air tight separating partition between the drying material 'l and the sensitive material `l. I

In this embodiment, when a ray of light enters the cell, a portion of the light may be .absorbed by the sensitive material Il to produce the desired electrical/ response, while another portion b may passV through the sensitive material l. The portionv bis, however, reflected back by the reflector S, and is incident upon the sensitive material l on the reverse side from the portion a. Most of the reflected portion b isv then absorbed in the sensitive material'to produce yan added eifect. Furthermorabecause of the inherentI surfacev reflection of glass, any small parts of reflected light b whichvare not completely absorbed may be re- `minor iniiuences upon the light-sensitive material. 'I'his `device thusincreases the effect of a given light intensity upon a light-sensitive Acell, o

and raises'the output ratio. t, f Alternatively,'a second layer of' light-sensitive 55 material may be provided to receive the trans'- mitted light. Referring to Figure 2, a plurality of glass plates or slips II and I2 may be provided upon which are positioned two pairs of electrodes I4 and I5, andl I5 and I'I. These pairs of electrodes, which may desirably be of platinum, are arranged with interdigitatedportions as described in connection with Fig. l, which portions are also covered with layers of light-sensitive material I8 and I9. An annular member 2l, which may conveniently be a short length of glass tubing is provided and attached by cement 22 in such a position as to bring the sensitive layers I8 and I9 within the annular member. Drying material 23 is also provided as before. Connection may be made to the respective electrodes in any convenient way, as by spring clamps or soldered connections or other means as desired, ,f

In the operation vof this embodiment, any light incident upon one of the light-sensitive layers or .units which is not absorbed, but transmited, is received by the other of the layers, to produce an added eiect in the circuit, if the two units are connected together. Alternatively, the second 4unit may be utilized to produce a second output in a separate circuit, for such uses as monitoring or other purposes. y,

Alternatively the electrodes and layer of sensitive material may be positioned upon opposite sides of a glass member, and the incident light applied toan edge of the glass member. Multiple internal reflection is then utilized'to obtain a maximum light action on the sensitive material. This embodiment is shown in Fig. 3 in which a glass plate or slip,25 is provided as before, and an auxiliary glass plate or slip 26, or a pluralityof such plates as shown, may be provided with interdigi'tated pairs of electrodes 2Iiand 28 preferably of platinum upon opposite sides. The interdigitated portions are covered with layers of sensitive material 3| and 32. 'Ihe auxiliary plate members 26'may be cemented to the plate member 25 in any convenient way as by Canada Balsam or other suitable cementing means. Alternatively, the auxiliary plates may be merely held in contact, although a loss of light may occur under these conditions from surface. reflections.

It is desirable that the plate members 26 be attached at an angle as shown, in order to provide a area for the entrance of light, and for similar reasons the plurality of auxiliary plates may be used. A protecting cup member 33 is desirably attached to the plate 25, over the plates 26, by means of cement 3l, and the drying material 35 is included within the cup 33 as before.

In the operation of this cell, the light ray enters the cell from the plate 25 as shown, and by a plurality of surface' reflections at the interface between the glass and the sensitive material, it is reected back and forth in the glass plate, and is thus incident a plurality of times upon the light-sensitive material. In this way a maximum utilization of the incident light is obtained, and a minimum amount of light is wasted from transmission and other losses.

In this embodiment as before, connection may be made to the electrodes 21 and 28 in any convenient way, as by spring clamps, or soldered leads, 36 which may be brought through the cup member 33 in any suitable manner.

This invention thus provides a simple and convenient means, including ysrious methods of utilizing reflecting means and a plurality of sensitive coatings for the better and more emcient utilization of light in the light-sensitive cell, to produce a greater response ratio, thereby obtaining a more enlcient and effective cell, as well as a new and useful cell construction.

While the above disclosure shows but a limited number of embodiments of the invention, it is possible to lproduce still further embodiments without departing from the inventive concept herein disclosed and it is therefore -desired that only suchvlimitations shall Ibe imposed upon the appended claim as are statedtherein or required bythe prior art.

The invention claimed is: f

A light-sensitive cell comprising a plurality of pairs of electrodes and layers of sensitive mate-` rial cooperating therewith, in cooperative relation to a single transparent support said electrodes comprising means adapted to reflect light to and between said sensitive layers.

' ARTHUR W. CARPENTER. 

